Chapter 9: Linear Momentum

Question 1

An object cannot be treated as a single particle when it either ___ or ___.

Answer 1

Rotates; deforms/changes shape.

Question 2

The center of mass (COM) of a system of particles moves as if___ and ___.

Answer 2

All the mass of the system were concentrated on the COM; all external forces acting on the system are concentrated on the COM.

Question 3

To calculate the COM for a system of N particles of total mass M:

Answer 3

(mi(yi) + mi2(yi2) + mi3(yi3) + …)/M

Question 4

There (must)/(need not) be actual physical mass at the location of the COM.

Answer 4

Need not

Question 5

The COM is biased towards the particles with the (greater)/(lesser) mass.

Answer 5

Greater

Question 6

Newton’s Second Law for the motion of COM:

Answer 6

a(arrowsubcom) = (F(arrowsubnetext))/M

Question 7

What is the linear momentum of a particle of mass m and velocity v(arrow)?

Answer 7

ρ = mv
SI unit: kg * m/s

Question 8

Is linear momentum a vector quantity?

Answer 8

Yes!

Question 9

TRUE or FALSE: F(subnet) = ma(arrow) = m((dv)/(dt)) = (d/(dt)(mv(arrow)) = (dρ(arrow))/(dt)

Answer 9

True!

Question 10

For position, velocity, and acceleration of the COM:

Answer 10

Use the same equation as that used to calculate the COM, substituting the position values with the independent velocity or acceleration velocities to suit your needs.

Question 11

Impulse (J) is as follows: J(arrowsubnet) = (dρ(arrow))/dt = Δρ(arrow). Graphically, this is the ___ on a ___ graph.

Answer 11

Area under the curve on a force vs. time graph.

Question 12

If the net external force on a system equals zero, then ρ(arrow) is…

Answer 12

Constant

Question 13

If an object is falling towards Earth’s surface, and the system ONLY includes the object, momentum (is)/(is not) constant.

Answer 13

Is not

Question 14

If an object is falling towards Earth’s surface, and the system includes both the object AND Earth, linear momentum (is)/(is not) constant, because F(arrowsubgrav) is internal, and both objects would therefore have (the same)/(different) momentum, meaning (one)/(both) have a velocity directed towards the other.

Answer 14

Is; the same; both.

Question 15

With collisions in Chapter 9, there is no external force on the system. Therefore, ΔP = …

Answer 15

0; P(subix) = P(subfx)
m(sub1)v(sub1i) + m(sub2)v(sub2i) = m(sub1)v(sub1f) + m(sub2)v(sub2f)

Question 16

In ___ collisions, total kinetic energy is the same before and after the collision.

Answer 16

Elastic

Question 17

Velocity 1 Final in elastic collisions in one direction:

Answer 17

((m(sub1)-m(sub2))/(m(sub1)+m(sub2)) * V(sub1i) + ((2m(sub2))/(m(sub1)+m(sub2)) * v(sub2i)

Question 18

Velocity 2 Final in elastic collisions in one dimension:

Answer 18

((m(sub2)-m(sub1))/(m(sub2)+m(sub1)) * V(sub2i) + ((2m(sub1))/(m(sub1)+m(sub2)) * v(sub1i)